This invention relates to biaxially oriented, heatset hollow multilayer containers wherein the containers comprise at least one layer containing poly(ethylene)terephthalate and at least one layer containing a high barrier copolyester formed from isophthalic or terephthalic acid, ethylene glycol and 1,3,bis(2-hydroxyethyoxy)benzene.
Containers suitable for use in beverage and food packaging applications require an optimal balance of several physical properties. Such containers must be able to withstand the high temperatures reached in hot fill food applications. Also, such containers must have sufficient barrier properties in order to provide a container with an acceptable shelf-like without deterioration of the beverage or food product. Further, it is desirable that such containers be optically clear.
In order to improve several physical properties of hollow articles such as bottles, the bottles have been made from multiple layers of thermoplastic resins. For example, the Yamada et al, U.S. Pat. No. 4,082,854 discloses a multilayer plastic material having at least one layer composed of an ethlenevinyl alcohol copolymer. While the Yamada et al '854 packaging material has acceptable oxygen barrier properties and may be used for hot fill applications, the packaging material lacks optical clarity. Therefore, the use of such packaging material to package food items is restricted to instances where optical clarity is not important.
Yamada et al, U.S. Pat. No. 4,182,457, discloses a multilayer container in which a polypropylene resin layer is oriented in order to improve upon optical clarity of the container. While the optical clarity of such containers is improved by the orientation of the resin layer, such containers lack adequate mechanical strength properties for use in storing carbonated beverages. Also, the containers are not suitable for hot fill applications since the polypropylene materials start to deform and shrink at relatively low onset-of-shrinkage temperatures. Further, these containers generally require an adhesive layer interposed between the oriented thermoplastic resin and the oxygen barrier layer.
Accordingly, there is a need in the art for an improved multilayer hollow article, and in particular a container, which has improved gas barrier properties, good interlayer adhesion without the need for an adhesive layer, desirable mechanical strength properties, optical clarity, and improved thermal stability such that the optically clear multilayer article may be used in hot fill applications.